The present invention relates to a device for inhibiting the use of a coin on a string to defraud a coin acceptor.
Users who wish to defraud a coin acceptor have been known to attach a thin string to a coin and to insert the coin into the coin acceptor. The presence of a genuine coin with the timing of a genuine coin causes the coin sensor checking the coin to judge the coin to be genuine and to move the coin to an acceptance area. An acceptance switch causes genuine coins to move to an acceptance channel for delivery to a coin box and causes all other articles to move to a rejection channel for return to the user. A coin sensor arranged downstream from the acceptance switch generates a credit signal when a coin passes through the acceptance channel toward the coin box. However, when a coin is attached to a string, the coin is not supplied to the coin box but rather the user tries to draw the coin back to the coin slot or a point above the acceptance switch so that the coin can be manipulated into the rejection channel and improperly retrieved.
Another technique for defrauding a coin acceptor is to attach a genuine coin to one end of a string and to attach a counterfeit coin or disk to the other end. The genuine coin is inserted first and, after it has been accepted for credit, the counterfeit coin is inserted. The counterfeit coin is rejected back to the user through the rejection channel. The user tries to manipulate the string attached to the counterfeit coin to improperly retrieve the genuine coin.
Prior designs have addressed this stringing problem. German Application Nos. DE 39 29 729 and DE 41 17 096 and EPO Application No. EP 0 358 946 show a lever or similar mechanism which is moved by a string attached to a coin. The string prevents the lever from returning to its original position. The position of the lever is optically sensed for the purpose of transmitting a signal to a control and evaluation circuit which detects stringing based on the position of the lever.
German Application No. DE 27 33 636 shows a string catching mechanism in a coin acceptor which retains the string and, consequently, the coin to prevent the latter from giving a signal to the credit memory. In practice, it has been found that the elements used to catch and retain the thin and light string must be mechanically sensitive and they may be easily damaged when a force is exerted on the string. Damage to the string catching mechanism may render it inoperable and may even block the coin travel path thus necessitating a service call. The above-described devices for preventing a string manipulation are also relatively sensitive.
German Application No. G 92 00 559.3 shows a heater for a coin acceptor which cuts a string thermoelectrically. The heater is switched on and off in response to a pressure switch in the area of the heating element. This requires additional expense and, in any event, may be circumvented by a clever manipulation.